When a storage battery such as a lithium ion secondary battery or a lead storage battery is placed in a charge state in a harsh temperature environment, battery capacity deterioration easily progresses. In particular, the battery capacity deterioration is remarkable in a full-charge state where a state of charge (SOC) is 100% (refer to FIGS. 7 and 8). For this reason, it is preferable that the storage battery is used in a mild temperature environment (in a normal temperature environment), for example, approximately from −10° C. to 50° C.
In Patent Document 1, an electric source device including a secondary battery, and a capacitor connected to the secondary battery in parallel is disclosed. The electric source device includes a detection unit detecting a temperature of the capacitor and a voltage of the capacitor, a switching element limiting a discharge current from the capacitor on the basis of a detection value of the detection unit, and a switching element performing at least one of limitation and blocking with respect to the charge current to the capacitor on the basis of the detection value of the detection unit. When the temperature of the capacitor is greater than or equal to a temperature threshold value set in advance (a lower limit of the temperature which is determined as being abnormal), the electric source device capacitor is disconnected. By such control, temperature information and deterioration of the capacitor are suppressed.
In Patent Document 2, a battery pack which is able to reduce possibility that a secondary battery is changed at a temperature unsuitable for the charge and is deteriorated regardless of whether a temperature of the secondary battery is a low temperature or a high temperature is disclosed. The battery pack includes a secondary battery, a connection terminal for receiving a charge current output from a charge unit which outputs the charge current for charging the secondary battery, a temperature detection unit detecting a temperature of the secondary battery, and a charge voltage control unit making the charge voltage of the secondary battery based on the current received by the connection terminal lower than a first voltage set in advance as a voltage for setting the secondary battery to be in constant-voltage charge when the temperature of the secondary battery detected by the temperature detection unit is a second temperature different from a first temperature set in advance as a temperature suitable for the charge of the secondary battery.